From 729e91cef7670f12f87d351024bda8a3f6eb17b1 Mon Sep 17 00:00:00 2001
From: Nikolay Bryskin <nikicat@users.noreply.github.com>
Date: Fri, 3 Apr 2026 17:49:44 +0300
Subject: [PATCH 1/2] fix: accept readonly arrays in LogTopic type

LogTopic now includes `readonly Hex[]` so that `as const` and readonly
arrays are assignable to topic filters without type errors.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>
---
 src/types/contract.test-d.ts | 42 ++++++++++++++++++------------------
 src/types/contract.ts        |  4 ++--
 src/types/misc.ts            |  2 +-
 3 files changed, 24 insertions(+), 24 deletions(-)

diff --git a/src/types/contract.test-d.ts b/src/types/contract.test-d.ts
index 25e269d98b..bb9fd0a03a 100644
--- a/src/types/contract.test-d.ts
+++ b/src/types/contract.test-d.ts
@@ -215,10 +215,10 @@ test('GetEventArgs', () => {
     'Transfer'
   >
   expectTypeOf<Result['from']>().toEqualTypeOf<
-    `0x${string}` | `0x${string}`[] | null | undefined
+    `0x${string}` | readonly `0x${string}`[] | null | undefined
   >()
   expectTypeOf<Result['to']>().toEqualTypeOf<
-    `0x${string}` | `0x${string}`[] | null | undefined
+    `0x${string}` | readonly `0x${string}`[] | null | undefined
   >()
 })
 
@@ -260,7 +260,7 @@ test('GetValue', () => {
 
 test('LogTopicType', () => {
   expectTypeOf<LogTopicType<string, Hex>>().toEqualTypeOf<string>()
-  expectTypeOf<LogTopicType<string, Hex[]>>().toEqualTypeOf<string[]>()
+  expectTypeOf<LogTopicType<string, Hex[]>>().toEqualTypeOf<readonly string[]>()
   expectTypeOf<LogTopicType<string, null>>().toEqualTypeOf<null>()
 
   expectTypeOf<LogTopicType<string, Hex | null>>().toEqualTypeOf<
@@ -271,7 +271,7 @@ test('LogTopicType', () => {
 test('AbiEventParameterToPrimitiveType', () => {
   expectTypeOf<
     AbiEventParameterToPrimitiveType<{ name: 'foo'; type: 'string' }>
-  >().toEqualTypeOf<string | string[] | null>()
+  >().toEqualTypeOf<string | readonly string[] | null>()
   expectTypeOf<
     AbiEventParameterToPrimitiveType<
       { name: 'foo'; type: 'string' },
@@ -286,7 +286,7 @@ test('AbiEventTopicToPrimitiveType', () => {
   >().toEqualTypeOf<`0x${string}`>()
   expectTypeOf<
     AbiEventTopicToPrimitiveType<{ name: 'foo'; type: 'string' }, Hex[]>
-  >().toEqualTypeOf<`0x${string}`[][]>() // TODO: Is this correct?
+  >().toEqualTypeOf<readonly `0x${string}`[][]>() // TODO: Is this correct?
   expectTypeOf<
     AbiEventTopicToPrimitiveType<{ name: 'foo'; type: 'string' }, null>
   >().toEqualTypeOf<null>()
@@ -300,7 +300,7 @@ test('AbiEventTopicToPrimitiveType', () => {
   >().toEqualTypeOf<boolean>()
   expectTypeOf<
     AbiEventTopicToPrimitiveType<{ name: 'foo'; type: 'bool' }, Hex[]>
-  >().toEqualTypeOf<boolean[]>()
+  >().toEqualTypeOf<readonly boolean[]>()
 })
 
 test('AbiEventParametersToPrimitiveTypes', () => {
@@ -310,7 +310,7 @@ test('AbiEventParametersToPrimitiveTypes', () => {
       [{ name: 'foo'; type: 'string'; indexed: true }]
     >
   >().toEqualTypeOf<{
-    foo?: string | string[] | null | undefined
+    foo?: string | readonly string[] | null | undefined
   }>()
   expectTypeOf<
     AbiEventParametersToPrimitiveTypes<
@@ -321,8 +321,8 @@ test('AbiEventParametersToPrimitiveTypes', () => {
       ]
     >
   >().toEqualTypeOf<{
-    foo?: string | string[] | null | undefined
-    bar?: number | number[] | null | undefined
+    foo?: string | readonly string[] | null | undefined
+    bar?: number | readonly number[] | null | undefined
   }>()
 
   type Named_AllowNonIndexed = AbiEventParametersToPrimitiveTypes<
@@ -338,9 +338,9 @@ test('AbiEventParametersToPrimitiveTypes', () => {
     }
   >
   expectTypeOf<Named_AllowNonIndexed>().toEqualTypeOf<{
-    foo?: string | string[] | null | undefined
-    bar?: number | number[] | null | undefined
-    baz?: `0x${string}` | `0x${string}`[] | null | undefined
+    foo?: string | readonly string[] | null | undefined
+    bar?: number | readonly number[] | null | undefined
+    baz?: `0x${string}` | readonly `0x${string}`[] | null | undefined
   }>()
   type Named_DisableUnion = AbiEventParametersToPrimitiveTypes<
     [
@@ -373,8 +373,8 @@ test('AbiEventParametersToPrimitiveTypes', () => {
     >
   >().toEqualTypeOf<
     | readonly []
-    | readonly [string | string[] | null]
-    | readonly [string | string[] | null, number | number[] | null]
+    | readonly [string | readonly string[] | null]
+    | readonly [string | readonly string[] | null, number | readonly number[] | null]
   >()
 
   type Unnamed_AllowNonIndexed = AbiEventParametersToPrimitiveTypes<
@@ -391,12 +391,12 @@ test('AbiEventParametersToPrimitiveTypes', () => {
   >
   expectTypeOf<Unnamed_AllowNonIndexed>().toEqualTypeOf<
     | readonly []
-    | readonly [string | string[] | null]
-    | readonly [string | string[] | null, number | number[] | null]
+    | readonly [string | readonly string[] | null]
+    | readonly [string | readonly string[] | null, number | readonly number[] | null]
     | readonly [
-        string | string[] | null,
-        number | number[] | null,
-        `0x${string}` | `0x${string}`[] | null,
+        string | readonly string[] | null,
+        number | readonly number[] | null,
+        `0x${string}` | readonly `0x${string}`[] | null,
       ]
   >()
 
@@ -426,7 +426,7 @@ test('AbiEventParametersToPrimitiveTypes', () => {
     >
   >().toEqualTypeOf<
     | readonly []
-    | readonly [string | string[] | null]
-    | readonly [string | string[] | null, number | number[] | null]
+    | readonly [string | readonly string[] | null]
+    | readonly [string | readonly string[] | null, number | readonly number[] | null]
   >()
 })
diff --git a/src/types/contract.ts b/src/types/contract.ts
index 4cbbf9a854..0f95e42c6f 100644
--- a/src/types/contract.ts
+++ b/src/types/contract.ts
@@ -466,8 +466,8 @@ export type LogTopicType<
   topic extends LogTopic = LogTopic,
 > = topic extends Hex
   ? primitiveType
-  : topic extends Hex[]
-    ? primitiveType[]
+  : topic extends readonly Hex[]
+    ? readonly primitiveType[]
     : topic extends null
       ? null
       : never
diff --git a/src/types/misc.ts b/src/types/misc.ts
index 625ba085cc..fdffe13618 100644
--- a/src/types/misc.ts
+++ b/src/types/misc.ts
@@ -3,7 +3,7 @@ import type { OneOf } from './utils.js'
 export type ByteArray = Uint8Array
 export type Hex = `0x${string}`
 export type Hash = `0x${string}`
-export type LogTopic = Hex | Hex[] | null
+export type LogTopic = Hex | readonly Hex[] | null
 export type SignableMessage =
   | string
   | {

From eb2eec6f1c9318ad7187bb0d3f9323dc32e12502 Mon Sep 17 00:00:00 2001
From: jxom <7336481+jxom@users.noreply.github.com>
Date: Tue, 21 Apr 2026 11:44:17 +1000
Subject: [PATCH 2/2] chore: add changeset

Amp-Thread-ID: https://ampcode.com/threads/T-019dad44-c9b7-73fd-9c97-2ffe6794479e
---
 .changeset/readonly-log-topic.md | 5 +++++
 1 file changed, 5 insertions(+)
 create mode 100644 .changeset/readonly-log-topic.md

diff --git a/.changeset/readonly-log-topic.md b/.changeset/readonly-log-topic.md
new file mode 100644
index 0000000000..286980592b
--- /dev/null
+++ b/.changeset/readonly-log-topic.md
@@ -0,0 +1,5 @@
+---
+"viem": patch
+---
+
+Fixed `LogTopic` type to accept readonly arrays.